1. Field of the Invention
The present relates generally to a shroud for a marine propulsion system which acts as a portable dry dock to remove at least portions of the marine propulsion system from the water.
2. Description of the Related Art
In marine propulsion systems, a portion of the propulsion system is submerged in the body of water in which the boat floats. It is desirable that the portions of the marine propulsion system in the water be removed from the water when the boat is not in use. Outboard motors accommodate this need by being capable of tilting to lift the propeller and other parts of the motor out of the water. It is then possible to flush the internal passageways of the outboard motor using, for example, a garden hose attachment.
An inboard marine propulsion system has only the propeller and the propeller drive shaft submerged in the water and so the problems associated with leaving the propulsion system in the water are minimized. This is particularly true since the inboard systems generally have a closed cooling system.
Inboard/outboard marine propulsion systems, on the other hand, have an outboard portion which is generally not capable of being tilted out of the water and which has bearings, gears, shafts and many other intricate internal parts. Although some inboard/outboard propulsion systems have lower, outboard units which can be tilted, it is generally not recommended that the outboard unit be left in a tilted up position since this can result in damage to the rubber bellows and seals in the unit.
Although some inboard/outboard propulsion systems have a closed cooling system which does not allow external water to circulate through the engine, even these units provide for circulation of sea water through the lower, outboard unit, the exhaust manifolds, and the heat exchanger.
The problems associated with a submerged outboard unit are particularly aggravated in salt water since rapid deterioration of the submerged lower unit can occur. In particular, electrolysis caused by dissimilar metals in the construction of the submerged unit causes decomposition as a result of electrical currents passing through the dissimilar metal parts. To overcome this problem, it has been common practice to provide sacrificial zinc anodic heads in the lower unit in various locations to minimize deterioration of the metal parts. As the anodic heads deteriorate, they must be replaced, sometimes as often as every three months when used in salt water. Salt water also causes deterioration and pitting of aluminum parts, including aluminum casings, or housings, and also causes corrosion problems with steel and cast iron components within the engine and manifolds.
A further problem with leaving the outboard portion in salt water is that salt water barnacles attach themselves to virtually any surface and can build up to a thickness of as much as two inches in a matter of weeks if not controlled. Although toxic, anti-fouling paints helps control barnacle build-up, it is not stopped entirely. Also, such anti-fouling paint is generally used only on the external surfaces of the lower unit, leaving the water intake holes and internal passageways of the unit to become clogged with barnacles, often in a few months time. Such clogged internal passageways cause impeller damage and engine overheating.
To combat the foregoing problems, it is currently the practice to remove the boat from the water when not in use so that the cooling system can be flushed and so that deterioration and barnacle build-up is prevented. The boat can either be placed on a trailer and thereby pulled from the water or the boat may be lifted from the water with a lift at a marina for placement in dry storage, or dry dock.
To remove the boat by a trailer after each use requires a considerable outlay of time, energy and money. Boat ramp fees must be paid, ramp availability must be considered as well as ramp opening and closing hours, travel time and expense in conveying the boat by trailer to the ramp locations and in loading and unloading equipment is to be considered, as well as such other factors as tide tables and the like. All of this can take the enjoyment out of a day's fishing or boating excursion.
When a marina lift is used to place the boat in the water and subsequently remove it, the business hours of the marina, which are usually from sun-up to sun-down must be considered as well as the waiting line or queue, of other boaters awaiting use of the lift. This can result in the boater being in the water and underway well after morning fishing is over, and it also requires that the day's activities be cut short in order to return to the marina before closing.
Boat owners not taking these precautions, including those whose boats which are too large to trailer or put in dry storage on a daily basis, are victims of high maintenance costs and frequent equipment failure.
The prior art includes U.S. Pat. No. 4,362,437 which discloses a device which may be attached to the hull of a ship in a liquid tight fashion so as to provide a water free volume in which work on the hull is done underwater.
A folding outboard motor cover and bracket to cover the upper portion of a motor is disclosed in U.S. Pat. No. 3,010,124.
An engine hood and slide therefor is disclosed in U.S. Pat. No. 1,100,216.